40 Questions
What is the primary way that a host cell can recognize the presence of a virus?
Detecting unusual elements of the viral genome, such as double-stranded RNA
What is the role of the enzyme Dicer in the response to viral infection?
To degrade double-stranded RNA into small fragments
What is the outcome of the binding of double-stranded RNA fragments to single-stranded RNA in the host cell?
The destruction of the single-stranded RNA
What are the two cytokines produced and secreted by the host cell in response to viral infection?
Interferon-a and interferon-b
What is the length of the double-stranded RNA fragments produced by the enzyme Dicer?
About 21-25 nucleotide pairs
What is the first step in the program of intracellular responses to eliminate viral RNA?
The degradation of double-stranded RNA into small fragments
Why are mammalian cells particularly adept at recognizing the presence of double-stranded RNA?
Because they have a highly effective innate immune response
What is the effect of interferons on protein synthesis in the host cell?
It shuts down most protein synthesis by phosphorylating and inactivating eIF-2
What is the purpose of the host cell's self-destruction by apoptosis?
To prevent the virus from replicating
What is the function of the protein encoded by the influenza virus?
To block the recognition of dsRNA by Dicer
What is the role of natural killer cells in the innate immune system?
To recognize and eliminate infected cells
What is the effect of some viruses on host cell apoptosis?
They inhibit apoptosis, which can have the side-effect of promoting cancer
What is the outcome when the host cell's measures to inhibit viral replication fail?
The cell takes the extreme step of killing itself by apoptosis
What is the effect of interferons on viral RNA?
They non-specifically degrade ssRNA
What is the common mechanism of killing infected target cells by NK cells and cytotoxic T lymphocytes?
Inducing apoptosis
What is the primary function of dendritic cells in the innate immune system?
To recognize and phagocytose invading pathogens
What is the result of dendritic cells cleaving pathogen proteins into peptide fragments?
The fragments bind to MHC proteins
What is the mechanism by which NK cells and cytotoxic T cells destroy virus-infected cells?
By inducing apoptosis in the infected cells
What is the location where activated dendritic cells activate T cells?
In a nearby lymphoid organ
What is the role of co-stimulatory proteins displayed on activated dendritic cells?
To activate T cells
What type of cell surface proteins do NK cells and cytotoxic T cells recognize to detect virus-infected cells?
Class I MHC proteins
How do cytotoxic T cells recognize virus-infected cells?
By recognizing peptide fragments of viral proteins bound to class I MHC proteins
What do cytokines secreted by activated dendritic cells influence?
The type of response made by T cells
Why do many viruses inhibit the expression of class I MHC proteins on the surface of infected cells?
To avoid detection by cytotoxic T cells
What is the outcome of the interaction between activated dendritic cells and T cells?
The T cells are activated to fight the pathogen
Which of the following viruses encodes proteins that block class I MHC gene transcription?
Adenovirus and HIV
What is the role of MHC proteins in the process of antigen presentation?
To carry peptide fragments to the cell surface
What is the main difference between how cytotoxic T cells and NK cells recognize virus-infected cells?
Cytotoxic T cells recognize peptide fragments of viral proteins, while NK cells recognize the level of class I MHC proteins
What is the link between the innate and adaptive immune systems provided by?
Dendritic cells
What is the outcome of NK cells selectively killing host cells that express low levels of class I MHC proteins?
The virus-infected cells and some cancer cells are selectively eliminated
What is the primary function of pattern recognition receptors on dendritic cells?
To recognize and phagocytose invading pathogens
What is the purpose of the co-stimulatory proteins displayed on activated dendritic cells?
To activate T cells of the adaptive immune system
What is the outcome of the interaction between dendritic cells and pathogens?
The dendritic cells are activated and phagocytose the pathogens
What is the role of MHC proteins in the process of antigen presentation?
To carry the peptide fragments to the cell surface
Where do activated dendritic cells activate T cells?
In the lymphoid organs such as lymph nodes
What is the outcome of the activation of T cells by dendritic cells?
The T cells are activated and join the battle against the specific invader
What is the role of cytokines secreted by activated dendritic cells?
To influence the type of response that the T cells make
What is the mechanism by which dendritic cells recognize and respond to pathogens?
Through the recognition of pattern recognition receptors and the activation of T cells
What is the link between the innate and adaptive immune systems provided by?
Dendritic cells
What is the outcome of the battle between the host and the pathogen?
The outcome depends on the specific pathogen and the host's immune response
Learn how virus-infected cells take drastic measures to prevent viral replication, and the role of natural killer cells and dendritic cells in the immune response. This quiz covers the importance of microbe-associated immunostimulants and the innate immune responses against viral pathogens.
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